How to Brush a Dog's Belly and Armpits

Get the dog lying on its side first, then work with the brush almost flat to the skin in short, light strokes, following the direction the hair grows. The belly and armpits have thin skin and almost no padding underneath, so the technique that works on a dog's back will hurt here.

These are the places mats start. Skin rubs on skin every time the dog walks, the hair is finer and softer than the coat on the back, and the whole area is out of sight, so a mat is usually a hard pad by the time anyone finds it.

Most owners brush the top of the dog, which is the part that looks groomed, and never touch the underside. That is why the first thing a groomer finds on a tidy-looking dog is a felted armpit.

The good news is that ten minutes a week on the underside prevents nearly all of it. The general technique for thin skin anywhere on the dog is set out in How to Brush a Dog Without Pulling the Skin, and everything below applies it to the hardest part of the dog to reach.

Why the Belly and Armpits Mat First

Three things happen in these areas that do not happen on the back, and together they make mats almost inevitable on a long or curly coat.

Constant friction. Every stride rubs the inside of the front leg against the chest and the inside of the back leg against the groin. Friction is what turns loose shed hair into a felted pad, and these are the only places on a dog where it happens thousands of times a day.

Softer hair. The coat on the underside is usually finer, softer and less protected by guard hairs than the coat on the back. Fine soft hair tangles faster and binds tighter.

Damp. The belly is the part that touches wet grass, puddles and snow, and the armpit holds moisture longer than anywhere else because air does not move through it. Damp hair that dries under friction is exactly how a mat forms.

Add the fact that nobody looks there, and a small tangle has weeks to become something that needs a groomer.

The Five Spots to Check Every Week

• The armpits. Where the front leg meets the chest. The single most common matting site on a dog.
• The groin and inner thighs. Same problem, rear end. Often worse on dogs that sit a lot.
• The chest, between the front legs. A deep pocket of coat that almost never gets brushed.
• The belly itself, especially around the navel. Thin coat, thin skin, picks up everything off the ground.
• Where the collar and harness sit. Not strictly the underside, but the same friction problem, and it hides under the strap.

Check all five with your fingers before you pick up a brush. You are feeling for anything that does not move freely when you lift it.

Getting a Dog Comfortable on Its Side

You cannot brush a belly properly on a standing dog. Reaching underneath means working blind, at an awkward angle, with your hand where the dog cannot see it, and that is how dogs learn to dislike the whole business.

Teach the position before you need it. Sit on the floor, ask for a down, and reward the dog for rolling onto one hip. Most dogs will tip onto their side from there within a few sessions if nothing unpleasant happens while they are there.

Work one side at a time and let the dog get up whenever it wants to. A dog that knows it can leave usually stays. A dog that has been held down once will remember.

For a dog that will not lie down, the fallback is to work with the dog standing and lift one front leg gently forward to open the armpit, doing a little at a time. Never hold a leg out at full stretch, and never roll a dog onto its back and pin it.

If your dog is genuinely frightened by being handled underneath, stop and build it up slowly over weeks with food. Forcing it turns a grooming problem into a handling problem that is much harder to fix.

Recommended Tools for Sensitive Underside Areas

Size is the whole story here. A large brush head cannot get into an armpit without the corner of the pad digging into the dog, and the armpit is the one place you most need to reach.

You also need a way to check your work, because the underside is where a brush most easily leaves felted hair behind while feeling like it has done the job.

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Flat Slicker Brush, Small

This is the one job on the dog where the small head is not a compromise, it is the correct tool. An armpit is a pocket a few inches across, and a large head simply will not sit in it without one edge pressing somewhere it should not.

The flat face matters as much as the size. A level pin field lets you lay the brush almost parallel to the skin, which is the only safe angle on a belly. A curved head presented flat puts its leading edge into the skin instead.

The pins are fine stainless steel with a slight bend near the tip and a smooth, burr-free finish. Fine enough to pass between soft hairs rather than dragging them, and smooth enough that repeated passes over thin skin do not score it.

The cushion pad flexes and returns. On the underside that is not a comfort feature, it is the thing that stops the pins driving in when they meet a knot over skin that has no muscle behind it.

Hold it in your fingertips rather than your palm for this work. You want to feel resistance the moment it happens, and a light grip is what gives you that.

• Best for: Armpits, groin, belly, behind the ears, and any small dog or cat.
• Why it works: A small flat head fits the pocket and can lie parallel to thin skin.
• Context: Light fingertip grip, short strokes with the hair, stop at the first resistance.

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Pawfect Potion 4-in-1 Shampoo

The underside is the dirtiest part of the dog and the part that gets washed least carefully, because most people are rinsing the back and the belly gets whatever runs down.

Friction is the reason this matters for brushing. Dry, gritty hair on the underside catches the pins, and catching is what makes the dog flinch and makes you stop early.

This formula cleans, conditions, detangles and moisturises in one pass. It is pH balanced for dogs and built on plant-derived cleansers from coconut, with organic aloe vera and coconut oil, plus lavender and chamomile.

Wash the belly and armpits deliberately, hands on, and rinse them for longer than you think. Shampoo left in a skin fold is a reason for a dog to lick and scratch an area that is already prone to trouble.

Then dry those folds properly before the dog lies down. A damp armpit under a dog's own body weight is the most reliable mat factory there is, and this is the single step most owners skip.

• Best for: Bellies, skin folds, dogs that walk in wet grass, and any coat that feels dry under the arms.
• Why it works: Lower friction means the pins pass through soft hair instead of snagging it.
• Context: Brush first, wash the underside properly, rinse well, dry the folds, brush again.

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Long Tooth Comb

On the underside the comb is doing something it does nowhere else on the dog. It is your eyes.

You cannot see an armpit while you are working in it, and fingers through a soft coat will miss a flat mat lying against the skin. A comb will not. It stops, and where it stops is the answer.

Run the wide teeth from skin to tip through each of the five areas before you brush and again after. Before, so you know what you are dealing with. After, so you know you actually cleared it rather than smoothing the surface.

The fine half is the one to use for the daily check. Drawn slowly over the skin it finds scabs, ticks, grass seeds between the back legs, and the firm feel of a lump that is not a mat at all.

That last point is worth taking seriously. Anything under the skin that does not move with the coat, or any area the dog reacts to sharply, is a reason to see a vet rather than a reason to keep brushing.

• Best for: Finding what your hands and eyes cannot on the underside of a dog.
• Why it works: Long teeth reach skin level, where underside mats actually sit.
• Context: Comb before, brush, comb again. Never force it through anything.

What the pins are doing inside the coat while all this happens is explained in What a Slicker Brush Actually Does to a Coat.

Step by Step: Brushing the Underside Safely

• Step 1. Get the dog onto its side on something soft, and sit where it can see your face.
• Step 2. Feel the whole underside with your fingers first. Find the tangles before the brush does.
• Step 3. Comb each area with the wide teeth to see what is actually there.
• Step 4. Open the armpit by moving the front leg gently forward. Support the leg, do not stretch it.
• Step 5. Lay the brush almost flat to the skin and draw it in short strokes the way the hair grows. A few centimetres at a time.
• Step 6. Use your free hand to hold the hair at its base, so any pull lands on your fingers and not on the dog's skin.
• Step 7. Work small tangles apart with your fingers first, from the outside edge inward, then brush.
• Step 8. Comb the area again from skin to tip. If the comb runs clean, move on.
• Step 9. Do the other side, then finish with something the dog enjoys so the position stays a good one.

Two or three minutes per area is plenty once there is nothing there. The long sessions only happen when it has been left.

When a Mat Is Already There

A tangle you can lift away from the skin and separate with your fingers is yours to deal with. Work from the outer edge inward, loosen a little at a time, and brush out what comes free.

A mat that lies flat against the skin and does not lift is not yours to deal with. Brushing it pulls the skin underneath, which on a belly or an armpit is thin, mobile and already sore.

Never cut a mat out with scissors in these areas. The skin lifts with the mat, you cannot see where one ends and the other begins, and belly and armpit lacerations from home scissor work are one of the most common grooming injuries vets see.

A groomer with clippers can take a flat mat off safely in under a minute. That is the right answer, and it is cheaper than the alternative.

Once the coat is clear again, keeping it that way is a weekly habit rather than a project. The general version of that habit is in Mat Prevention Tips for Dogs | Complete Grooming Guide.

Common Mistakes on a Dog's Underside

Brushing at the same angle as you do the back. Pins presented at forty-five degrees into thin skin is how brush burn happens. Flat to the skin, always.

Using the big brush because it is the one in your hand. The corner of a large pad in an armpit is sharp, and the dog will tell you about it once and then avoid you.

Holding the leg out to get better access. Shoulders do not enjoy being stretched. Move the leg a little, work, let it go back.

Working on a wet or damp underside. Water tightens every tangle it touches. Brush out first, then wash.

Pushing through when the dog tenses. Tensing is information. Stop, feel what is under the brush, and find out whether it is a mat or something that needs a vet.

Only doing it when you notice a problem. By the time an armpit mat is noticeable from outside, it has been forming for weeks.

FAQs

Why does my dog hate having its belly brushed?

Usually because it has hurt before. Thin skin, a brush held at the wrong angle, or a mat being pulled will teach a dog very quickly that the position is unpleasant. Rebuild it slowly with short sessions and food, and change the angle so the brush lies flat.

How often should I brush my dog's armpits?

Once a week for most coats, and two or three times a week for anything long, curly or doodle-type. It takes a couple of minutes per side when there is nothing there, which is the point of doing it regularly.

Can I use the same brush I use on my dog's back?

You can if it is small enough to sit inside the armpit without an edge pressing on skin. On most dogs that means a smaller head than the one you use on the body, and a flat face rather than a curved one.

Is it safe to cut a mat out of my dog's armpit?

No. The skin there is loose and lifts with the mat, so it is very easy to cut the dog without realising. A groomer can clip it off safely in seconds, and that is the right call every time.

What if I find a lump instead of a mat?

Stop and book a vet appointment. Anything firm that sits under the skin rather than in the coat, anything that does not move when you move the hair, or any spot your dog reacts to sharply is a question for a vet, not for a brush.

My dog's armpit skin is red and raw. What do I do?

Leave it alone and see a vet. Raw skin under a foreleg can be rubbing, a reaction, an infection or the aftermath of a mat, and brushing or washing it will not tell you which. Treat the skin first, groom the area once it has healed.

Does a harness cause matting?

It can, in exactly the same way a mat forms anywhere else, through friction over a fixed spot. Check under every strap when you do the underside, and take the harness off when the dog is not wearing it for a walk.

My dog will not lie down for grooming. What are my options?

Work standing, one small area at a time, lifting a front leg gently forward to open the armpit. It takes longer and you will do it in several sittings, which is fine. Teaching the side position with food over a few weeks is worth the effort if you have a long-coated dog.

Final Thoughts

The underside of a dog is where the coat work actually matters, and it is the part almost everyone skips. Friction, soft hair and damp make it the first place to mat, and being out of sight makes it the last place anyone looks.

The technique is not complicated. Get the dog comfortable on its side, use a brush small enough to fit, lay it flat to the skin, take short strokes with the hair, and check with a comb rather than trusting how it looks.

Do that once a week and the armpits stop being a problem. Leave it, and the next person to find out will be your groomer or your vet.